7912 Phones Screen On but No Dial Tone

Hi all,

I know that the Cisco 7912 phones are older phones, but we have about 200+ of them on campus, and they have been giving me a lot of issues lately. Specifically we have been having an error with the phones where:

When you unplug everything (PoE network) and reboot the phone it comes back fine.

This has been happening repeatedly to multiple phones across campus. We have tried to isolate it as a network issue, but our network consultant assures us our network is fine. Our phones are on the latest firmware available for that model.

Wait. I just tried looking

Wait. I just tried looking for the "span to PC" instructions for the 7912 model phones. But it says that the 7912 phones don't have that feature. So I don't think I will be able to do the packet capture.

Hi Hitesh,

Hi Hitesh,

I was finally able to mirror a port with one of the phones in the "no dial tone" state. I've attached the wireshark trace. 10.11.1.27 is the phone and 10.11.0.10 is our call manager. During the trace I picked up the handset (there was no dial tone) and tried calling a number. This is all I got out of my trace.

For the phone in question, I

For the phone in question, I checked the switchport and the phone shows up in the arp table. I checked the DHCP server and the phone actually has an IP address, it's just not registered in the call manager. I tried pinging the phone and looking at the phone's web interface, both work just fine.

But when I pick up the handset and dial, the trace doesn't even show the phone sending an "OffHook" command. What would cause the phone to do this? It is already on the latest firmware for a 7912 (ver 8.0.4).

I can't figure out why the phone isn't sending the "OffHook" request or how to fix it.

Just to clarify, are all 7912

Just to clarify, are all 7912 phones experiencing the issue, or only some of them?

When you say after power cycle the phone comes back fine, do you mean it registers and makes calls but then unregisters after a while?

Are the phones in 'no dial-tone state' showing as "Registered" or "Unregistered" in CUCM? In your original post you mentioned the phone display is normal when in 'no dial-tone' state, i.e. it shows extension and "Your current options". Does the phone show as 'Unregistered' in CUCM at that point (this would be unusual)?

What version of CUCM?

On the phone, hit Settings > Status > Status Messages. What messages do you see there?

On the phone's web interface, under Network Configuration, do all IP's look familiar? Does any of the 'Call Manager' say 'Active' next to them?

Can you reliably replicate the issue and collect packet capture as the phone is going into 'no dial-tone' state?

The issue is happening

The issue is happening randomly to 7912 phones across campus. We have 220 7912 phones. When everyone came back from Winter break, I had about 20 of them with this issue.

After you power cycle, the phone registers and works. But there have been phones who are repeat offenders, and others that aren't.

The phones show up as Unregistered in CUCM. But yes, on some of the phones the OSD shows normal, on some it is missing some options but still lit.

We are using CUCM System version: 10.5.2.10000-5.

Under the network configuration all the IP addresses (the DHCP, DNS, Gateway, etc are all correct). However, none of the Call Managers show as "Active" (there is 1 Passive and 1 with nothing next to it).

I cannot reliably replicate the issue. It just happens randomly to phones. People come in and pick up their handset and notice that there is no dialtone. After they reboot there are 5 voicemails waiting, so they don't know how long the phone as been offline.

Please confirm that the

Please confirm that the phones are always registering with the server listed first in their CUCM Group. Some phones may be assigned a different device pool, so it's ok for some phones to register to one node, and some to another, as long as that's the first node in their Device Pool's CUCM Group. If they register to a second node and don't re-register to the first node even after reset or power cycle, then that's an indication of a problem.

Forgot to ask, do you have other phone models in the cluster? Any issues with them?

Please run the following on CUCM Publisher:

utils ntp status

utils dbreplication runtimestate

utils diagnose test

Run the following on CUCM Subscriber:

utils ntp status

utils diagnose test

Keep an eye on 7912's in CUCM web gui and if you see any with a status of Unregistered, use RTMT to run unregistered phone report:

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